PIRL.Utilities
Class UNIX_Process

java.lang.Object
  java.lang.Process
      PIRL.Utilities.UNIX_Process

public class UNIX_Process
extends Process

A UNIX_Process is an adapter for the UNIXProcess implementation of the abstract Process class that provides access to hidden information.

The API for the Java Process class, as of Java 1.6, has an unfortunate shortcoming: The user is unable to access the process identification (PID) of the executed process nor provide the timeout argument to the Object.wait method used by the waitFor method. Process is an abstract class that is implemented by a host OS dependent class - UNIXProcess for UNIX systems - which relies on JNI methods that make the necessary host process management system calls.

For the UNIXProcess class (as of Java 1.6) the PID value is held in the private "pid" variable. UNIX_Process provides an ID() method to get the PID value.

The ability to provide the timeout argument is a trivial modification of the waitFor method. UNIX_Process provides a waitFor(long) method that limits the wait for the process to exit to a timeout value.

An exited() method provides direct access to the running/exited flag for the process.

All Process API methods are simply passed to the underlying Process.

Version:

1.4

Author:

Bradford Castalia - UA/PIRL

See Also:

Process

Field Summary

static String

ID Class identification name with source code version and date.

Constructor Summary

UNIX_Process(Process process)
Construct a UNIX_Process for a Process object on a UNIX system.

Method Summary

void	destroy()
boolean	exited() Test if the process has exited.
int	exitValue()
InputStream	getErrorStream()
InputStream	getInputStream()
OutputStream	getOutputStream()
int	ID() Get the Process ID that uniquely identifies the system process.
int	waitFor()
int	waitFor(long timeout) Wait for the process to exit up to a maximum timeout.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

ID

public static final String ID

Class identification name with source code version and date.

See Also:

Constant Field Values

Constructor Detail

UNIX_Process

public UNIX_Process(Process process)
             throws NoSuchFieldException,
                    SecurityException

Construct a UNIX_Process for a Process object on a UNIX system.

Parameters:

process - The Process object obtained from a ProcessBuilder's start method or a Runtime exec method.

Throws:

NoSuchFieldException - If the process does not have one of the expected field variables. This will occur if the process is not implemented by a JFC UNIXProcess or the implementation has changed from what is expected.

SecurityException - If a JVM SecurityManager prevents access to the private field values of the process object.

See Also:

ProcessBuilder, Runtime

Method Detail

getOutputStream

public OutputStream getOutputStream()

Specified by:

getOutputStream in class Process

getInputStream

public InputStream getInputStream()

Specified by:

getInputStream in class Process

getErrorStream

public InputStream getErrorStream()

Specified by:

getErrorStream in class Process

waitFor

public int waitFor()
            throws InterruptedException

Specified by:

waitFor in class Process

Throws:

InterruptedException

exitValue

public int exitValue()

Specified by:

exitValue in class Process

destroy

public void destroy()

Specified by:

destroy in class Process

ID

public int ID()

Get the Process ID that uniquely identifies the system process.

Returns:

the integer ID used by the system to identify the process.

waitFor

public int waitFor(long timeout)
            throws InterruptedException,
                   IOException

Wait for the process to exit up to a maximum timeout.

Causes the current thread to wait, if necessary, until the process represented by this Process object has terminated or the timeout period has expired. This method returns immediately if the subprocess has already terminated. If the subprocess has not yet terminated, the calling thread will be blocked. If the subprocess exits while the thread is blocked the exit status of the subprocess will be returned. If the timeout period expires while the thread is blocked an IOException will be thrown.

Parameters:

timeout - The maximum amount of time, in milliseconds, to wait on subprocess exit. Wait forever if the value is <= 0 (the same as the waitFor() method}.

Returns:

The exit value of the process.

Throws:

InterruptedException - If the current thread is interrupted by another thread while it is waiting, then the wait is ended and an InterruptedException is thrown.

IOException - If the timeout occurred before the process exit occurred.

exited

public boolean exited()

Test if the process has exited.

The running/exited flag will only be set true after the forked process has exited.

This method tests the value of the UNIXProcess flag. The Process API may be used to determine if the process has exited via the exitValue() method which will throw an IllegalThreadStateException if the process has not yet exited.

Returns:

true if the process has exited; false if it is still running.